Python: Make experimental/library-tests/CallGraph pass for Python 2

The import doesn't actually work the intended way, so running ``` $ python python/ql/test/experimental/library-tests/CallGraph/test.py ``` will procude no output. but our extractor will extract the things we need, so for a quick fix this will need to suffice.
2020-07-13 14:52:28 +02:00 · 2020-07-13 14:52:28 +02:00 · 83bd14b687
--- a/python/ql/test/experimental/library-tests/CallGraph/code/init.py
+++ b/python/ql/test/experimental/library-tests/CallGraph/code/init.py